Ants of Kenya
This webpage is the regional project page for Kenya. A list of species can be found here Kenya
The most recent study to assess the Kenyan ant fauna is: Hita Garcia, F.; Wiesel, E.; Fischer, G. 2013. The ants of Kenya (Hymenoptera: Formicidae) - faunal overview, first species checklist, bibliography, accounts for all genera, and discussion on taxonomy and zoogeography. Journal of East African Natural History 101:127-222. DOI: 10.2982/028.101.0201 This webpage is based on this publication. There are 596 species in 63 genera from 12 ant subfamilies known from Kenya.
Generic Diversity Table
The following table provides an accounting of the number of species for each genus. The last column of the table, Taxonomic Status, provides some idea of the taxonomic status of the genera. Good means that the number of species given here is likely a good estimate of the generic diversity, fair means revisionary work is needed but the genus is not likely to be much more diverse and poor indicates there remains much uncertainty in regards to the number of species for the genus. More information about each genus is also given in the text that follows this table. Links are provided that will easily move between the table and text for each entry.
Genera are organized by subfamily (listed in alphabetical order), and are listed in alphabetical order within each subfamily. The ordering of the rows can be changed to show other arrangements by clicking on a heading.
Genera are organized by subfamily (listed in alphabetical order), and are listed in alphabetical order within each subfamily.
The Old World genus Aenictus is distributed in the Afrotropical, Palaearctic, Oriental and Indo-Australian regions (Gotwald, 1982, 1995; Shattuck, 2008). Currently, it comprises 148 species worldwide, of which 40 are found in the Afrotropical region (Shattuck, 2008; Bolton, 2012). In Kenya there are six valid species, two subspecies and three unidentified morphospecies from Kakamega. These species numbers should however be regarded with caution, since the taxonomy of this genus is in a state of confusion. Most species were described on the basis of a single unassociated caste or sex. This might indicate that the real number of species is significantly lower since it is very likely that the unknown castes from an already described species were not adequately recognised but described as different species. Emery (1910) provided a list of the then known fauna, and some species or unknown sexual forms were described some decades ago (Gotwald & Cunningham-van Someren, 1976; Gotwald & Leroux, 1980; Campione et al., 1983). Nevertheless, no modern taxonomic revision is available for the Afrotropical region, and without keys the identification to species level is often difficult or impossible.
Aenictus are small, blind, monomorphic army ants that live in colonies with hundreds or thousands of workers and seem to be specialised predators of ants or other social insects (Wilson, 1964; Gotwald, 1982, 1995). Despite the large colony size, they are generally inconspicuous due to their hypogaeic lifestyle and appear to be comparatively rare on a local scale (Shattuck, 2008). Like other army ants, they display nomadism, and migrate to new nesting sites after depletion of prey colonies in their environment. Furthermore, Aenictus possesses specialised dichthadiiform queens with an increased egg-laying ability and new colonies arise through colony fission (Gotwald, 1982, 1995).
The genus Aenictogiton is of extraordinary interest within the Afrotropical region. The genus occurs in Central, South, and East Africa, and is biogeographically limited to the Afrotropical region (Brown, 1975; Parr et al., 2003; Hita Garcia et al., 2009). Material of Aenictogiton is generally scarce, and consists solely of male specimens. Brown (1975) already stated the complete lack of knowledge concerning the female castes, which, despite intensive search efforts, have not been discovered until the present day. The known species richness appears comparatively small, with just seven described species (Brown, 1975), although a good number of unidentifiable and possibly undescribed specimens located in several museum collections await taxonomic examination and possibly description as new species. The taxonomy of the genus can be regarded as unsatisfactory since it was never revised after the initial species descriptions (Emery, 1901; Forel, 1913; Santschi, 1919b, 1924). The only Kenyan species is an unidentified male-based morphospecies recorded from the Kakamega Forest.
The biology of this enigmatic genus remains an almost complete mystery. Brown (1975) mentioned the possibility that these ants are subterranean or otherwise strongly cryptobiotic; we fully agree since no foraging worker nor any trace of a colony could ever be found. Phylogenetic and morphological affinities to the army ant genus Dorylus suggest an army-ant-like lifestyle, although there is no current evidence for this. However, most males were collected from light traps close to forest localities, indicating that Aenictogiton might prefer forested habitats.
The genus Stigmatomma is of global distribution and holds currently around 60 described species (Yoshimura & Fisher, 2012). Since Brown (1960) it was considered to be a junior synonym of Amblyopone Erichson, but it was recently revived to genus rank (Yoshimura & Fisher, 2012). In the Afrotropics it seems to be relatively species-poor with only three described species (Brown, 1960; Gotwald & Levieux, 1972), but it should be mentioned that more than 13 undescribed forms exist in several museum collections (Brian Fisher, personal communication). Two unidentifiable and possibly undescribed species are known from the Kenyan coast. Although Brown (1960) reviewed the genus (as Amblyopone) on a global basis, he did not provide a revision of the Afrotropical fauna. One species was described later, but outside of a generic framework (Gotwald & Levieux, 1972). As a consequence, the genus is in need of a modern taxonomic revisionary work.
Members of this genus, as most amblyoponines, are specialised predators, which are thought to hold several ancestral anatomical and behavioural character states (Fisher, 2003). Stigmatomma species are known to live a hypogaeic lifestyle as predators of chilopods (Gotwald & Levieux, 1972) and in addition, are known as "dracula ants" that feed on their own larvae (Fisher, 2003; Saux et al., 2004). Queens can be observed to perform a form of non-destructive cannibalism by cutting a hole in the larval integument to feed on the exuding hemolymph. This however does not seem to harm the larvae, which continue growing and eventually emerge as normal adults.
The genus Cerapachys is widely distributed across the World's tropics and subtropics, although most of the 146 known species occur in the Old World (Brown, 1975; Bolton, 2012). Although treated by Brown (1975) on a global base, the taxonomy of this genus is far from satisfactory, especially for the Afrotropical region. Brown (1975) listed around 20 described species from this region and presented an identification key to the worker caste, but postponed a formal revision until more material would become available. He also presented some doubts on the species status of some species, and mentioned the existence of several undescribed species. Unfortunately, since then no more works on Afrotropical Cerapachys have been published. Consequently, the identification to species level with Brown's (1975) key is often unreliable. At present, we recognise eight valid species and two morphospecies for Kenya.
Cerapachys ants are specialised predators of other ants that conduct raids to attack prey nests. They retrieve captured larvae and pupae, less commonly also adults, to their own colony and store them as food (Hölldobler, 1982; Brown, 1975). Wilson (1958) and later Brown (1975) raised the question of whether Cerapachys and other members of the subfamily are nomadic, and proposing that nomadism might have evolved as special adaptation in ant-hunting cerapachyines in order to avoid depletion of prey. Members of this genus can be encountered in a variety of habitats ranging from humid rainforests to arid savannah grasslands or semi-deserts, and nests are generally constructed in the ground or in rotten wood (Brown, 1975).
Simopone is distributed in the Afrotropical, Malagasy, Oriental, and Indo-Australian regions and it holds 38 described species (Brown, 1975; Kutter, 1976, 1977; Bolton & Fisher, 2012), of which most are found in the Afrotropical and Malagasy regions. In their recent revision of the genus Bolton and Fisher (2012) list 18 species for the Afrotropical region. Currently, three species are known to occur in Kenya, which are only known from the Kakamega Forest. On the basis of the recent revision by Bolton and Fisher (2012), the taxonomy of the genus is in an excellent condition, and very good identification keys are now available for workers and queens.
Simopone seem to be rare, arboreal ants and presumably nocturnal (Bolton, 1973a; Brown, 1975; Kutter, 1977; Bolton & Fisher, 2012). Knowledge on the natural history of most species is very limited, but from some species it is known that they are specialised predators of other ants (Brown, 1975; Bolton & Fisher, 2012).
Although Sphinctomyrmex occurs in the tropics of the New and Old World, only 22 described species are known and these are mainly distributed in Australia (Brown, 1975; Bolton, 2012). Brown (1975) listed just two valid species for the Afrotropical region, but mentioned another three undescribed species. Unfortunately, the two described species are only known from males and the other species mentioned by Brown remain undescribed until today. Additionally, in Kenya two unidentified and probably new worker-based species were sampled in the Kakamega Forest. As a consequence, it is not possible to identify any worker-based Sphinctomyrmex from the Afrotropical region, and a modern taxonomic revision that associates workers, queens, and males is highly desirable.
Unfortunately, knowledge on the ecology of the African species is fairly limited. They appear to be rare ants that nest in the ground or rotten wood and were mainly collected from the leaf litter (Bolton, 1973a; Brown, 1975). Some species from Australia seem to be comparatively army-ant-like and have more or less dichthadiiform queens; these species perform mass raids on other ants and are presumably nomadic (Brown, 1975; Buschinger et al., 1990).
Axinidris is endemic to the Afrotropical region, and seems to be zoogeographically mostly restricted to the Guineo-Congolian rainforest belt from West Africa to the Kakamega Forest in Western Kenya, with few species occurring also in Eastern or Southern Africa (Snelling, 2007). A total of 21 species are known (Bolton, 2012). Interestingly, all eight species known from Kenya are only found in the Kakamega Forest in Western Kenya (Snelling, 2007; Hita Garcia et al., 2009) and four of these are also endemic to this rainforest. This genus is in an almost perfect taxonomic situation, with a revision by Shattuck (1991) and a more recent one by Snelling (2007), allowing easy identification to species.
The genus Axinidris is an arboreal genus with an omnivorous diet (Shattuck, 1991; Snelling, 2007) and its members seem to prefer moist rainforest habitats where they nest in hollow, living or dead stems, or in rotten wood (Snelling, 2007).
The genus Tapinoma comprises 64 described species that are distributed worldwide (Bolton, 2012). The Afrotropical region holds 13 described species (Robertson, 2000). There are four valid species and two subspecies known from Kenya and we found two additional morphospecies from Arabuko Sokoke. Species level identification of African species is generally problematic due to the lack of any modern taxonomic revisionary works.
Most Tapinoma species are arboreal and some live in close associations with myrmecophyte plants (Wheeler, 1922; Bolton, 1973a). In addition, they seem to be generalised foragers (Brown, 2000).
Technomyrmex is of moderate size with 93 described species, which are distributed throughout all tropical and sub-tropical zones, mainly in the Afrotropical, Oriental and Indo-Australian regions (Bolton, 2012). Around one third of them occur in sub-Saharan Africa, from which 25 are endemic to this region (Bolton, 2007), and, at present, we recognise nine valid and one undescribed species from Kenya. Recently, Bolton (2007) revised the genus for the West Palaearctic and Afrotropical regions and presented a key to the worker caste.
The majority of Technomyrmex species nest and forage arboreally or sub-arboreally and even the few species that nest in soil or leaf litter forage on trunks and in the canopy (Bolton, 2007). Some specialised myrmecophilous plants have been reported to house Technomyrmex species (Hölldobler & Wilson, 1990), but to what extent this might be true for the Kenyan species remains unknown. The diet mainly consists of hemipteran honeydew, though most species also feed on dead or living arthropods or their brood (Bolton, 2007).
This genus is distributed throughout the Old World tropics and subtropics, but the majority of species are found in the Afrotropical zoogeographical region (Gotwald, 1982, 1995). The taxonomic condition of Dorylus, especially for the African continent, can be classified as chaotic and useless for identification purposes. On a global basis, 59 species and 68 subspecies are recognised (Bolton, 2012), although the taxonomic validity of many of these taxa is highly questionable. The problem is that most descriptions were based on a single caste, and careful examination of taxa in order to find evidence for conspecificity among these is very rare (Schöning et al., 2008). Also, no modern taxonomic revision is available, which dramatically increases the difficulties to identify Dorylus to species level. Nevertheless, identification to subgenus level can be well performed with the keys provided in Gotwald (1982). At present, we recognise around 15 species, seven subspecies and two morphospecies from Kenya but this number will likely change with future taxonomic modifications and new discoveries.
The army ant genus Dorylus is mostly known for the spectacular swarm raids performed by some epigaeic species, mostly belonging to the subgenus Anomma, better known as "driver ants". These species perform huge swarm raids along the ground and lower vegetation with hundreds of thousands of blind, polymorphic workers to hunt down a great variety of prey taxa in large quantities, predominantly invertebrates (Gotwald, 1982, 1995). However, many more species within the genus live and hunt hypogaeicly and these army ants are generally less visible than their epigaeic relatives (Berghoff et al., 2002). Hypogaeic species hunt in columns and many species are known to be specialised predators of other social insects, such as termites or other ants (Darlington, 1985; Gotwald, 1982, 1995; Schöning & Moffett, 2007). Almost all species of Dorylus, like other army ant genera, live in monogynous colonies with dichthadiiform queens that have a massive egg-laying capacity, e.g. three to four million eggs per month in “driver ant” queens (Raignier & van Boven, 1955). In addition, Dorylus colonies migrate in irregular intervals to new nesting sites and new colonies emerge through colony fission (Gotwald, 1982, 1995).
Despite their cryptic lifestyle Acropyga, are found in all zoogeographical regions and at present 40 species are known (LaPolla, 2004a; Bolton, 2012). The genus was recently globally revised and just three species are recognised from the Afrotropical region (LaPolla, 2004a; LaPolla & Fisher 2005). LaPolla and Fisher (2005) drew attention to this seemingly depauperate Afrotropical Acropyga diversity, especially when compared with the over a dozen species known from the Oriental and Neotropical regions. Whether this low diversity is typical for the Afrotropics or just a sampling artefact due to insufficient collecting still remains unclear. All three Afrotropical species can be well identified with the key provided in LaPolla & Fisher (2005). Only one species, Acropyga silvestrii , which is widespread in the whole Afrotropical region, is known from Kenya (Hita Garcia et al., 2009).
Acropyga are usually small, cryptic, slow-moving ants that live a hypogaeic lifestyle predominantly in forest habitats (Prins, 1982; LaPolla & Fisher, 2005). The genus is also well known for its close association with mealybugs that are tended for their honeydew on underground plant roots (LaPolla et al., 2002). This relationship is so close that virgin queens take along a mealybug between their mandibles when they leave their birth nest to establish a new colony. (LaPolla et al., 2002; LaPolla & Fisher, 2005).
Anoplolepis is a relatively small genus with only nine valid species (Bolton, 2012), which are predominantly distributed in the Afrotropical region, with fewer species in the Malagasy and Oriental regions and some introduced in other regions. Only one species is listed from Kenya, namely Anoplolepis custodiens, which shows a wide distribution range from Southern Africa to Kenya and Somalia (Prins, 1982). This species is also known as the "common pugnacious ant" because of its aggressiveness and fast movements. It is very common in South African orchards and vineyards (Prins, 1982) where it was early regarded as a pest (Arnold, 1922). There is no modern revision available for this genus on an Afrotropical basis, although Prins (1982) presented a taxonomic treatment for the South African species. Unfortunately, he only provided a key to the queen and male castes.
These formicines are epigaeic and active ants that forage on the ground or the vegetation. Their diet is comparatively variable since they feed on a variety of small arthropods but also on honeydew produced by aphids or coccids (Prins, 1982).
Camponotus is an extremely large and complex, globally distributed genus. At present, more than 1000 species and nearly 500 subspecies belonging to 45 subgenera are described (Bolton, 2012) and it could well be the largest ant genus of all. Robertson (2000) listed around 150 species for the Afrotropical region and we recognise around 48 Kenyan species, subspecies, and morphospecies. However, all these species counts do not likely represent the "real" number of species found in nature. The enormous species richness, high levels of intraspecific and geographic variation and polymorphism render the taxonomy of Camponotus one of the most complex and difficult. Revisionary studies on Camponotus are generally confined to species groups and / or small geographical regions (e.g. Robertson & Zachariades, 1997; Snelling, 2006; McArthur, 2007; Shattuck & Janda, 2009). The Afrotropical species were treated by several authors in the past (Wheeler, 1922; Emery, 1925a; Santschi, 1926a; Bernard, 1953), but none of these authors tried to fully revise the genus. The only modern treatment for this region is the revision of a small species group restricted to Southern Africa by Robertson & Zachariades (1997). The majority of species, however, remain in a state of taxonomic confusion and would strongly benefit from a modern revision.
These ants live in a variety of habitats and microhabitats and the sheer size of the genus makes any characterisation of their biology challenging. In the Afrotropical region they are almost ubiquitous, occurring from humid rainforests to arid savannahs and from the ground to the canopy. Nests are built in the ground, in rotten branches or twigs, or rarely into living wood (Bolton, 1973a) and most species possess a highly generalistic diet.
The genus Lepisiota is distributed in the Old World and with 81 described species of moderate size (Bolton, 2012). The Afrotropical region harbours 45 species (Robertson, 2000; Bolton, 2012) and we list eight valid species and one subspecies from Kenya. However, these species counts have to be taken with caution since there are 21 additional unidentified morphospecies from the country, as well as several dozen more morphospecies from other Afrotropical localities located in museum collections (F.H.G. & G.F., unpublished data). The taxonomy of this genus is in an awful condition because it was never revised for the region. Forel (1892) provided a key to a few then known species but the usefulness of this key is limited since it covers only a minor fraction of the current diversity. Later, Wheeler (1922) and then Emery (1925b) published diagnoses and catalogues of the genus, although none of them attempted a full revision. No further taxonomic works were published since then and a modern revision of Lepisiota would strongly improve the taxonomic understanding of Afrotropical formicines. The "real" number of Kenyan species is very likely to be less than the 29 listed here. It is very difficult to assign names to morphospecies and this situation can only be improved by examining type material.
Generally, Lepisiota nest in rotten wood, in the ground, or in standing trees, and can be considered as generalised foragers (Bolton, 1973a; Brown, 2000). They are especially abundant in less forested habitats, such as grasslands, savannahs or woodlands.
Although it reaches its highest diversity in the tropics, Nylanderia is distributed worldwide and holds currently more than 130 species (LaPolla et al., 2011a). The taxonomic history of the genus can be characterised as changeful and unstable. Nylanderia was originally described as a subgenus of Prenolepis, then either treated as a subgenus of Paratrechina (Emery, 1925b), as a good genus (e.g. Wheeler, 1936a), or until lately as a synonym of Paratrechina (Trager 1984). This unsatisfying situation was changed by LaPolla et al. (2010a) who raised Nylanderia to genus rank on the basis of molecular data, and clarified the taxonomic and phylogenetic situation within the Prenolepis genus group. Recently, LaPolla et al. (2011b) revised the Afrotropical Nylanderia fauna and provided a key to species. Four valid species are known from Kenya.
Nylanderia are able to live in a variety of habitats, ranging from deserts to rainforests (LaPolla et al., 2011a). They nest in leaf litter, soil, or in rotten wood, and most species are epigaeic, generalist foragers (LaPolla et al., 2011a).
Currently, only two species of Oecophylla “weaver ants” are known: one from the Oriental and Indo-Australian regions and another one from the Afrotropics. The “red tree ant”, Oecophylla longinoda, occurs in the latter region, and is spread throughout the whole of sub-Saharan Africa (Weber, 1949c). Despite the large popularity of the genus (Hölldobler & Wilson, 1990), its taxonomy is in a very disappointing condition since it has not yet benefited from a modern taxonomic revision. Both species together contain 12 subspecies (Bolton, 2012), and it is unclear whether some of these merit species status or should just be regarded as junior synonyms. Oecophylla longinoda and one subspecies, Oecophylla longinoda textor, are listed for Kenya, and we cannot rule out that the status of both names might change in the future. It is possible that O. longinoda textor represents a good species, but it could also just be a synonym of the nominal species.
The weaver ant O. longinoda is one of the most popular and well-studied ants from the Afrotropical region (Hölldobler & Lumsden, 1980; Hölldobler & Wilson, 1990). It is one of the dominant species in African forest canopies and is especially known for its “weaver ant” ability to bind tree leaves into nest compartments with silk spun by larvae (Hölldobler & Lumbsen, 1980). One colony with more than 500,000 individuals can built hundreds of nests in several trees, which are aggressively defended against other conspecific colonies or other ants (Hölldobler, 1979; Hölldobler & Wilson, 1990). They are predacious and hunt large insect prey, not only in the canopy but also in the surrounding vegetation or on the ground and in addition, they tend honeydew-producing insects to supplement their diet (Weber, 1949c; Hölldobler & Lumbsen, 1980).
Paraparatrechina is biogeographically restricted to the tropics of Africa, Asia and Australia (LaPolla et al., 2010a). Thirty species are known from these regions, of which ten occur in the Afrotropical region and three in Kenya (LaPolla et al., 2010b). The genus, originally described as a subgenus of Paratrechina Motschoulsky, and last treated as a synonym of Paratrechina (Trager, 1984), was raised to genus rank in 2010 (LaPolla et al., 2010a). The taxonomy of the Afrotropical fauna was revised by LaPolla et al. (2010b).
The Afrotropical species can be found in rainforests and forest clearings, in the leaf litter or in rotten logs, and some species presumably live in the vegetation or the canopy (LaPolla et al., 2010b). Paraparatrechina are generalistic feeders and often live in trophobiotic relationships with hemipterans (LaPolla et al., 2010a).
The genus Paratrechina contains the single worldwide occurring tramp species Paratrechina longicornis, which is a successful invader predominantly distributed throughout the World’s tropics and subtropics, but is also found in many temperate localities as an indoor pest (Wetterer, 2008). The recent phylogenetic and taxonomic treatments on the Prenolepis genus group (LaPolla et al., 2010a, b) included several modifications at genus level that rendered Paratrechina monotypic and re-elevated Nylanderia and Paraparatrechina. Since P. longicornis is the single species in the genus, the identification is straightforward with the key to genera published in LaPolla et al. (2010a).
This species is well known as a household, greenhouse, and agricultural pest and seems to prefer semi-natural or disturbed habitats (Wetterer, 2008). It often enhances the population of phloem-feeding hemipterans that can cause serious damage to plants and it can reduce the arthropod diversity of particular habitats (Wetterer, 1999, 2008).
Plagiolepis, with 57 valid species (Bolton, 2012), is a genus of moderate size. It is restricted to the tropical and temperate regions of the Old World and 18 species occur in the Afrotropical region (Robertson, 2000). Five valid species are listed for Kenya, as well as an additional morphospecies from Kakamega. No modern revision or a key to species exist, which is a serious obstacle for the identification of Plagiolepis species.
Unfortunately, also very little is known about the biology of the Afrotropical species. They are small formicines nesting on trees, rotten wood, twigs, or in the soil (Bolton, 1973a).
This genus is one of the largest within the subfamily Formicinae with currently 614 listed species, which occur in the Old World’s tropics and subtropics, except in the Malagasy region (Bolton, 1973b, 2012). The central distribution of the genus is certainly in the Oriental and Indo-Australian regions whereas it plays a less important role in the Afrotropical region. The latter region holds only 43 valid species (Bolton, 1973b; Robertson, 2000) and we list nine for Kenya, with an additional morphospecies. A revision of the Afrotropical species with a good key to the worker caste was provided by Bolton (1973b).
Due to its sheer size Polyrhachis has a diverse ecology. They live in different forests or savannahs (Bolton, 1973b), and nest in trees, in or on the ground, in plant cavities, or within rock crevices (Robson & Kohout, 2007). Some species are weaver ants and build pavilions with larval or spider silk, while other species are social parasites of other ants and live within the colonies of their hosts (Maschwitz et al., 2003). Many species live in trophobiotic relationships with aphids or coccids (Liefke et al., 1998), but there are many species without trophobiotic partners that feed on floral and extra-floral nectarines, sugary saps of fruits and trees, on dead or living insect prey, or get their electrolytes in form of vertebrate excrements.
Tapinolepis is a small, species-poor genus with just 14 species restricted to the Afrotropical and Malagasy regions (Bolton, 2012). Until the last decade Tapinolepis was regarded as a synonym of Anoplolepis, but was reinstated as a good genus by Bolton (2003). Revisions or keys treating Tapinolepis as a genus have not been published yet. Only one morphospecies sampled in Nairobi is known from Kenya.
Unfortunately, the biology of the Afrotropical species is completely unknown.
Over 40 species of Leptanilla are known (Bolton, 2012), which are largely distributed in the Old World tropics and subtropics (Baroni Urbani, 1977; Bolton, 1990; Lopez et al., 1994). Baroni Urbani (1977) revised the genus on a global basis, and he recognized three species from the Afrotropical region. However, the Afrotropical material was comparatively scarce, and from two species only the male caste is known. The real species number for this region will probably turn out to be higher with several undescribed species located in museum collections (Bolton, 1990). Furthermore, sampling methods that specifically target hypogaeic insects (Normand, 1911; Lopez et al., 1994) might very likely discover more species of these cryptic ants. One unidentified species was recently recorded from a Western Kenyan rainforest (Hita Garcia et al., 2009), but it is still unclear if this might be an undescribed species or the worker caste of a male-based species.
The members of this genus are all very small, pale, subterranean ants that are rarely collected, especially the worker and queen castes. Leptanilla species nest and forage in the ground, and seem to be specialised predators of geophilomorph centipedes (Masuko, 1990). Additionally, the queens of some species are known to feed on their larvae, but unlike amblyoponine queens they do not damage the larval integument. Instead the larvae possess a specialised duct organ on the fourth abdominal segment from which the queens can gain the larval haemolymph (Bolton, 1990; Masuko, 1990). Leptanilla displays several behavioural similarities to army ants since all known queens are dichthadiiform, several species are known to be migratory, and foraging is performed in groups.
Atopomyrmex is endemic to the Afrotropical zoogeographical region and with only three species is a relatively small genus. Nevertheless, the distribution of the genus extends to much of Sub-Saharan Africa, and one species, Atopomyrmex mocquerysi, is known from Kenya. The genus was revised by Bolton (1981a) who recognised two species, and a third was later described by Snelling (1992). Species identification can be easily performed with the species key from Bolton (1981a) and the diagnostic notes in Snelling (1992).
The members of the genus are highly polymorphic, arboreal ants that nest in living wood (Bolton, 1981a; Kenne et al., 2009). From one species it is known that its wood-excavating nest activities cause the tree branches to dry out (Kenne et al., 2009). Atopomyrmex ants forage in the vegetation or on the ground and their diet is variable since it can consist of honeydew or small arthropods. In addition, they seem to prefer the canopy stratum of secondary forests or woodlands, but are only rarely encountered in old growth forests (Kenne et al, 2009; F.H.G. & G.F., unpublished data).
The genus Baracidris is very species-poor with just three described species, which are endemic to the Afrotropical region (Bolton, 1981a; Fernández, 2003; Bolton, 2012). One species, Baracidris pilosa, is known to occur in Kenya, although the only existing specimen was destroyed during transport from one museum to another (see Fernández, 2003). Therefore, it is strongly desirable to rediscover and collect more material of this genus. The genus was revised by Bolton (1981a), who recognised two West African species and later Fernández (2003) described a third species from Uganda and Kenya and updated the species key from Bolton's previous work.
Not much is known about the natural history of these rare ants. All three species seem to inhabit forest habitats and were mainly collected from leaf litter (Fernández, 2003).
Calyptomyrmex is a comparatively small genus with 37 described species (Bolton, 2012) distributed throughout the Afrotropical, Malagasy, Oriental and Indo-Australian regions (Baroni Urbani, 1975; Bolton, 1981b; Shattuck, 2011). Sixteen species are known from the Afrotropical region (Bolton 1981b) and six occur in Kenya. Interestingly, almost all specimens were collected in the Kakamega Forest. The taxonomy of the genus was revised by Bolton (1981b) who included a good key to the worker caste.
Species of this more cryptic genus are typically found in the leaf-litter stratum or in the soil of forest habitats. They forage individually or in small groups of two or three workers and in several species the foragers "play dead" if disturbed and remain motionless for a while (Bolton, 1981b; F.H.G., personal observations). A remarkable characteristic of most Calyptomyrmex is their possession of bizarre, often extremely so, pilosity, which can be scale-like, spatulate, clavate, or teardrop-like. At present, there is no explanation for these very specialised forms of pilosity.
This genus occurs worldwide with 67 species (Bolton, 2012) and possesses several successful tramp species (Seifert, 2003). At present, the Afrotropical fauna consists of 11 described species (Rigato, 2002). Three valid species are known from Kenya of which two are known to be invasive (Heinze et al., 2006) and two further morphospecies were found in the Kakamega Forest. The taxonomic situation for the Afrotropical region is in a relatively good condition, with a revision and keys for the whole region (Bolton, 1982; Rigato, 2002).
Cardiocondyla are often inconspicuous ants because they usually nest subterraneously and live in relatively small colonies of up to a few hundred individuals (Heinze et al., 2006). Most species prefer anthropogenically or naturally disturbed open and arid habitats (Seifert, 2003). Foraging is commonly performed solitarily and most species are omnivorous. One interesting aspect of the biology of the genus is the rare presence of long-living ergatoid males that mate intranidally and usually kill other ergatoid males in order to monopolise matings (Heinze & Hölldobler, 1993; Seifert, 2003; Heinze et al., 2006).
The taxonomy of Carebara has seen great improvements on both generic and regional levels during the last decade (Fernández, 2004, 2006, 2010). Of high importance was Fernández' (2004) synonymisation of the former genera Afroxyidris, Oligomyrmex and Paedalgus under Carebara. Nonetheless, the taxonomy of the genus in the Afrotropics is to a great extent either outdated or fragmentary. Santschi (1914) and Wheeler (1922) treated parts of Oligomyrmex and Carebara. Weber (1950) revised the then known members of Oligomyrmex, and provided a species key for the major caste. Also, there is a key available for species formerly classified as Paedalgus (Bolton & Belshaw, 1993). However, the works of Santschi (1914), Wheeler (1922), and Weber (1950) are very outdated and the whole genus, with 160 species (Bolton, 2012), would benefit highly from an updated revision. We list ten species and one subspecies of Carebara under its recent definition for Kenya, but there are also eight morphospecies and most of them are probably undescribed.
Most species in this genus are small, cryptic, hypogaeic ants that nest in the soil, the leaf litter or in termite mounds. The latter is important since some species seem to be lestobiotic (Bolton & Belshaw, 1993). Some species show an extreme size dimorphism between the tiny worker and the very large queen caste that led to the theory that young queens transport workers to the new nest site to assist with the foundation of a new colony (Arnold, 1916; Wheeler, 1936b). However, on the basis of observations on queens of one species, Lepage & Darlington (1984) and later Robertson and Villet (1989) did not find any evidence for this theory.
The genus is of Palaeotropical distribution with its main diversity centred in the Afrotropical region where 35 species from the global total of 65 exist (Bolton, 1974a, 2012). Of these, 15 are known from Kenya. Most seem to be restricted to the rainforest habitats in Western Kenya around Kakamega, but this could also be a sampling artefact. The taxonomy of the genus is in a fairly good condition since it was first revised by Bolton (1974a) on a global scale, additional species added later by Snelling (1979) for the Afrotropical region and then Bolton (1982) presented an updated revision with more new species and a species-level key.
Most species of this genus are forest-inhabitants while only a minority live in more open and arid habitats. All nest and forage on trees or in the vegetation and several species are known to be trophobiotic, while one species was observed to prey on termites (Arnold, 1917; Bolton, 1974a). Interestingly, many members of this genus often co-occur with more dominant and aggressive ant species from the genera Crematogaster and Oecophylla but are usually well-protected by their heavily armoured exterior or dropping-off behaviour (Bolton, 1974a; Yanoviak et al., 2008).
The ant genus Crematogaster is one of the most species-rich and widely distributed genera worldwide, with approximately 470 valid species and 300 subspecies (Bolton, 2012). Despite its cosmopolitan distribution, most species are found in the tropics. More than 130 taxa are scattered across the whole Afrotropical region. The extreme species richness together with the high intraspecific and geographical variability provides serious obstacles for the taxonomic understanding of this genus. Thus, it is not surprising that revisionary treatments are very scarce and have been thoroughly avoided in the past. Some regional faunas have been revised on genus or subgenus level (Buren, 1959; Longino, 2003; Hosoishi & Ogata, 2008, 2009; Blaimer, 2010, 2011), but the Afrotropical Crematogaster fauna remains in great need of a taxonomic revision. Therefore, species level identifications of most Kenyan species are comparatively problematic and only possible through comparisons with well identified reference or type material. We list 22 species, 18 subspecies and 12 morphospecies for Kenya, but the "real" number of species is very likely to be lower than their sum of 52.
In tropical regions, most members of this genus are arboreal (Longino, 2003), although a minority of species nest and forage on the ground (Quinet et al., 2009; Hosoishi et al., 2010). Crematogaster can be found in a diversity of habitats, such as forests, woodlands, savannahs or shrublands (Blaimer, 2010) and they often play a dominant, aggressive and territorial role within the local ant fauna (Longino, 2003). Concerning their food sources, most Crematogaster seem to be highly generalistic and omnivorous (Longino, 2003), although the most important resource for many species is homopteran honeydew.
This is a relatively rare and small genus with just four described species, all of which are restricted to tropical Africa (Bolton, 1981a). Only one species, Cyphoidris spinosa, is known from the Kakamega Forest. The taxonomy of Cyphoidris was treated in Bolton (1981a). The identification to species level is comparatively easy with the identification key presented by Bolton (1981a).
The biology of these four species is relatively mysterious except that they prefer the leaf litter stratum in Equatorial rainforests.
Dicroaspis is a minute genus endemic to the Afrotropical region. In his revision of the genus Bolton (1981b) recognised only two valid species and suggested that even these might be variations of the same form. A further, unidentified species was found in the Kakamega Forest (Espira, 2001), which represents the only record of Dicroaspis in Kenya.
The biology of this genus remains to a great extent unknown, although collection data suggests that these ants live in the leaf litter of rainforests.
Melissotarsus is an extremely rarely encountered genus with only four described species distributed in the Afrotropical and Malagasy regions (Bolton, 2012). Two of them are listed for Kenya. The Afrotropical species were revised by Bolton (1982) who also provided a good species identification key.
These ants are special in several ways. They build their nests in healthy wood by tunnelling through the living tissue beneath the surface (Bolton, 1982; Fisher & Robertson, 1999; Belshaw & Bolton, 1994) and are rarely encountered outside of their nests, which could be the main reason for their relative scarcity in museum collections (Bolton, 1982). Also, they live in close association with symbiotic coccids that are kept inside the nest and furthermore, the adults are able to produce silk, which is used to close exit holes or to seal cracks (Fisher & Robertson, 1999).
This genus contains 81 species (Bolton, 2012) and is distributed throughout the Old World tropics but its main diversity is centred in Australia (Andersen, 2006). Only a few species occur in the Oriental region or in Africa. Of the eight Afrotropical species, most are restricted to Southern Africa, while only two have a wide distribution across Africa and are also found in Kenya (Bolton, 1981b). For the Afrotropical region the taxonomy of the genus is in a good state due to the revision of Bolton (1981b), which includes an effective species identification key.
The African species of this genus nest in the ground, in rotten wood, or under stones (Bolton, 1981b). Foraging is performed primarily on the ground or in the leaf litter whereas only very few species may additionally climb up trees or shrubs (Bolton, 1981b). Anderson (2006) indicated that the Australian species of this genus are either omnivorous, opportunistically feeding on seeds, or specialised granivores. When disturbed they show a special ‘faking-death’ behaviour. They retract their antennae into the scrobes, tuck their legs under the promesonotal shield and remain motionless (Hölldobler, 1988).
The genus is of moderate size with approximately 110 known species (Bolton, 2012), which are distributed across the Holarctic, Afrotropical, and Oriental regions, with its highest diversity found in the Palaearctic region. The Afrotropical region holds a comparatively small proportion of 13 species, of which four occur in Kenya (Bolton, 1982; Ferrer & Collingwood, 1993). The then known species were revised by Bolton (1982), who also provided a key to the medium-sized and large workers. However, the key does not cover all species, since Messor ferreri Collingwood was described later from Kenya (Ferrer & Collingwood, 1993).
Messor is a genus of primarily granivorous ants that play an important role in seed dispersal. These ants are commonly encountered in savannahs, grasslands, or even more arid habitats like semi-deserts and deserts (Bolton, 1982).
Microdaceton is a relatively species-poor genus with only four described species that are endemic to the Afrotropical region (Bolton, 2000, 2012). Of these, two species occur in Kenya (Bolton, 2000; Hita Garcia et al., 2009). The taxonomy of Microdaceton, as well as for the whole tribe Dacetini, is in a fairly good condition, since it was well revised in recent decades (Bolton, 1983, 1999, 2000). All African species are easy to identify with the species level key provided by Bolton (2000).
Species of this genus are relatively uncommon dacetine ants that nest in the leaf litter stratum. Apart from this no other information about their biology is known so far.
Monomorium is a comparatively large and widely distributed genus. Currently it holds a total of 384 valid species (Bolton, 1987, 2012; Heterick, 2006). Bolton (1987) listed 145 species for the Afrotropical region, though the synonymisation of four African species (Heterick, 2006) reduced the species count to 141. Presently, 33 described species are known from Kenya and we also found five potentially undescribed morphospecies. Despite the seemingly well-treated taxonomy of the genus in several parts or zoogeographic regions of the world (e.g. Bolton, 1987; Collingwood & Agosti, 1996; Heterick, 2001, 2006), the genus definition of Monomorium is far from satisfactory (Heterick, 2006). Future taxonomic work at genus-rank level might split up the genus into smaller, better-defined genera. However, under the current genus definition, the species level key from Bolton (1987) allows a proper identification of most Afrotropical and Kenyan species.
Considering the wide distribution and species richness, it is not surprising that Monomorium are found in many terrestrial habitats and microhabitats. Astonishingly, very little is known of the natural history of most species (Ettershank, 1966). Feeding habits of most species seem to be generalistic, or more rarely granivorous. Several species are lestobiotic or parasitic and in addition, some species belong to the most successful and broadly distributed ant tramps (Ettershank, 1966; Bolton, 1987).
A total of 32 species of Myrmicaria (Bolton, 2012) can be found throughout the Afrotropical, Oriental and Indo-Australian zoogeographical regions, though the largest number occurs in the Afrotropics. The genus is distributed throughout Africa, which holds 22 described species (Santschi, 1925; Bolton, 2012). Two species and four subspecies are listed for Kenya. Arnold (1916) was the first to try to disentangle the taxonomy of this genus and he provided a key to the South African species. Unfortunately, his key is limited to Southern Africa, and surely outdated. Later, Santschi (1925) treated the taxonomy of all African Myrmicaria species and he included a diagnosis, lists of known taxa and a species level key for the worker caste, but by today’s standards, his revision is certainly outdated and we recommend being cautious with his species key.
In the Afrotropical region these ants seem to prefer open habitats where they can be locally quite abundant. They nest in the soil, and foraging is performed alone or in smaller groups (Levieux, 1983). Based on observations on one species (Levieux, 1983), members of the genus seem to be mostly carnivorous, with a diet consisting of a variety of insects, especially termites and ants and supplemented by homopteran honeydew.
Nesomyrmex, formerly a subgenus of the large and almost cosmopolitan Leptothorax, was raised to genus in 2003 (Bolton, 2003) and 51 species can be encountered in the tropics and subtropics of the Neotropical, Malagasy and Afrotropical regions (Bolton, 2012). The latter region holds 25 species (Mbanyana & Roberson, 2008), of which four species are listed for Kenya. The Afrotropical Nesomyrmex species were first revised by Bolton (1982), back then as African members of Leptothorax and later Snelling (1992) described one additional species from Cameroon. Recently, Mbanyana & Roberson (2008) reviewed the genus for South Africa and added 15 new species. For the identification of Kenyan species one should combine the key in Bolton (1982), a later species description in Snelling (1992) and the key to southern African species (Mbanyana & Roberson, 2008).
The biology of the genus is not well studied. Most species prefer arid habitats while a few live in rainforests. Generally, Nesomyrmex ants can nest either in the soil, as most South African species do, or in trees (Mbanyana & Roberson, 2008), often in pre-existing cavities. However, the four Kenyan species all seem to be arboreal.
Ocymyrmex is another genus endemic to the Afrotropical region. It is biogeographically restricted to Southern and Eastern Africa whereas it seems to be absent from the forest zones of West and Central Africa and the sub-Saharan Sahelian Zone (Bolton & Marsh, 1989). Currently 37 species are known, most of which live in Southern Africa. Comparatively few species occur in East Africa, such as the three species listed for Kenya (Bolton & Marsh, 1989; Bolton 2012). However, we think that this small species count is mainly due to a sampling artefact since only very few collections were undertaken in the arid regions of the country. The taxonomy is in an excellent condition. Based on the taxonomic revision of Bolton (1981a), the genus was revised again by Bolton & Marsh (1989). The latter publication includes an excellent key to the worker caste. Bolton and Marsh (1989) mention three new species in press by Prins & Roux, but unfortunately, this paper was never published (Bolton, 2012).
This arid-adapted genus lives in dry savannahs or under desert conditions. All species nest in the ground and the colonies, which consist of 200 to 1000 individuals, are situated comparatively deep in the soil (Marsh, 1987; Bolton & Marsh, 1989). They move remarkably fast in the hottest part of the day (Arnold, 1916), which is surely an adaptation to the arid environment. Furthermore, one South African species was observed to forage individually and to lower their temperature, if necessary, by pausing at shaded spots or by climbing on objects to leave the desert ground for a while (Marsh, 1985). The main food source seems to consist of dead or heat-stressed insects, living termites and seeds (Bolton, 1981a; Marsh, 1986). Interestingly, all species possess ergatoid females that differ morphologically only very little from the workers (Bolton, 1981a). Despite the fact that many females are present in the colony, just one female is inseminated. So, the colony is functionally monogynous and the other, unmated, females have a worker-like behavioural repertoire (Forder & Marsh, 1989).
At present, Pheidole is one of the largest ant genera worldwide with approximately 980 described species and 142 subspecies (Longino, 2009; Bolton, 2012). Despite being such a hyper-diverse genus, only very few modern taxonomic revisions exist (e.g. Eguchi, 2001; Wilson, 2003; Sarnat, 2008; Longino, 2009; Fischer et al., 2012). Unfortunately, they focus on the New World, the Oriental or Indo-Australian regions, whereas the Afrotropical region remains without any taxonomic treatment. The latter region accounts for a rather modest count of 139 valid Pheidole species, subspecies, and varieties. The only revision available is the recent work on the Pheidole pulchella species group (Fischer et al., 2012). Species identifications outside this species group are problematic to impracticable and will only be simplified after more revisionary studies. In Kenya we recognize 15 species, three subspecies and 20 morphospecies. The total count of 38 might be higher than necessary since it is hard to assign names from older literature to modern morphospecies without the examination of types.
Pheidole workers are usually dimorphic, with a minor and a major worker caste. The genus is often referred to as generalized foragers and omnivorous ants, but the overall range of behavior and ecology is much more diverse. Many savannah and desert species are specialized seed harvesters (Burge, 2005; Carroll & Janzen, 1973), others can be plant mutualists (Fischer et al., 2003; Letourneau et al., 2004), while some seem to be more predatory (G.F., unpublished data). For many Afrotropical species, however, relatively little is known about their ecology and behaviour (Mertl et al., 2010).
With 57 recognised species the genus Pristomyrmex is of moderate size (Bolton, 2012). They are distributed in the Afrotropical, Malagasy, Oriental, and Indo-Australian regions, but also in smaller areas of the Palaearctic. Nevertheless, most species are found in the Oriental region (Wang, 2003; Zettel, 2006, 2007). Wang (2003) recognised only five African species, of which two occur in Kenya. The genus taxonomy is in a good state since both first Bolton (1981a), on an Afrotropical and later Wang (2003), on a global basis, revised the genus and provided good species keys.
On a global basis, most species of Pristomyrmex can be found in rainforests (Wang, 2003), although the Afrotropical representatives seem to be less restricted to this habitat and can be found in a variety of forest types and in more open woodlands (Bolton, 1981a). Their diet is most likely carnivorous and they nest in the soil, the leaf-litter, in rotten wood, or around plant roots (Taylor, 1965b; Bolton, 1981a; Wang, 2003). Interestingly, some species display "faking-death" behaviour if disturbed, and some species are nocturnal.
Solenopsis is a species-rich and virtually cosmopolitan genus. At present, 183 described species are known, which occur in all tropical and temperate regions worldwide (Bolton, 2012). The main distribution of the genus, however, is situated outside the Afrotropical region, where only 17 species occur (Ettershank, 1966). Ettershank (1966) provided a global species list and diagnosis of the genus, but modern revisions or keys to the Afrotropical species are not available. Only one valid species and subspecies are listed for Kenya, with an additional morphospecies from Kakamega.
The most famous and better-studied Solenopsis species are the larger, epigaeic, and often dominant, species commonly known as “fire ants”, but these are restricted to the New World (Ettershank, 1966). The Old World species are small and generally lestobiotic, cryptic or socially parasitic species. The known Kenyan species seem to be mostly subterranean and were only rarely found on the surface. Nests were found within the soil or in abandoned chambers of termite mounds. These observations are well in accordance with Arnold’s (1916) notes on Solenopsis punctaticeps.
Strumigenys is a very species-rich, worldwide occurring genus mainly distributed in the world tropics and subtropics (Bolton, 2000). The current genus definition includes both, the genus Strumigenys and the former genus Pyramica Roger, which was proposed as junior synonym of Strumigenys some years ago (Baroni Urbani, 2007). This latter work changed Strumigenys into one of the most diverse genera with 831 valid species (Bolton, 2012). There are around 130 species known from the Afrotropical region and at present we list 29 species and seven morphospecies for Kenya. The taxonomy of the whole tribe was exhaustively revised by Bolton (2000) on a global scale. The species level keys for Afrotropical Pyramica and Strumigenys provided in that work, together with Rigato (2006), allow a clear identification of most Kenyan species. Due to the high quality of Bolton's (2000) keys and descriptions, it is also fairly easy to identify the seven morphospecies as tentative new species.
Most Strumigenys species are small, cryptic ants that nest and forage in leaf litter, in soil, or in rotten wood, whereas there are far fewer genus members that prefer an arboreal life-style. Many species are specialised predators possessing trap-jaw mandibles, and mainly hunt collembolans or other small arthropods (Hölldobler & Wilson, 1990; Bolton, 1999).
Temnothorax is an almost worldwide distributed genus and relatively species-rich with around 330 species (Bolton, 2012). Most of them are distributed in the New World and in the Palearctic region, while just 11 species occur in the Afrotropical and Oriental regions (Radschenko, 2004). During most of its history Temnothorax was more or less regarded as either a subgenus or a junior synonym of Leptothorax (see Bolton, 2012 for references), but was redefined by Bolton (2003) and gained the status of a good genus. Only one species, Temnothorax cenatus, is known from Kenya (Bolton, 1981a).
Temnothorax species cover a wide range of habitats from cold forests to savannahs and semi-deserts (Radschenko, 2004). Some species are arboreal, whereas others nest in soil, leaf litter, or under stones (Radschenko, 2004). However, the biology of the Afrotropical members of the genus remains to a great extent unknown.
Terataner is a small genus with only 12 described species, restricted to the Afrotropical and Malagasy regions. A species list can be found in Bolton (1981a) who revised the six species occurring in the Afrotropical region and provided a key to the worker caste. Bolton (1981a) and later Alpert (1992) separated the African species into two groups. One comprises the four West African species and the other includes one East African and one South African species. The latter group is, with a few valid and numerous undescribed species, much more strongly represented in the Malagasy region. In Kenya the only known species is Terataner bottegoi, which seems to be restricted to the dry forests of the Kenyan coast.
The split of the genus into two groups is not only based on biogeography, but also on differences in nesting behaviour. While the West African species all nest in rotten parts of standing trees, generally at considerable height above ground, the East African, South African, and Malagasy species all nest near the ground and live in preformed plant cavities (Bolton, 1981a; Alpert, 1992). These cavities can be dead branches or twigs on the ground or in bushes. Most Terataner are predators of other arthropods, their larvae and often of other ants or termites (Alpert, 1992).
The genus Tetramorium is distributed worldwide, and with 465 valid species is comparatively diverse (Bolton, 2012). The Afrotropical region holds the largest species number currently with more than 220 described species (Bolton, 1976; Bolton, 1980; Hita Garcia et al., 2010a, 2010b, 2010c). At present, Kenya has a total of 41 described species and 20 morphospecies and the genus is by far the most species-rich for the country. On the basis of Bolton’s (1980) revision and the examination of most type material, it was possible to reveal that all encountered morphospecies represent undescribed forms. Some were recently described (Hita Garcia et al., 2010a, 2010b, 2010c) and the remainder will be treated in future publications.
Tetramorium is often one of or the most species-rich genus in Afrotropical ant communities, although it is not necessarily the most abundant. Members of this genus can be found in a wide range of habitats from humid rainforests to arid savannahs and deserts and in different strata from the ground and leaf litter layer to the high forest canopy (Bolton, 1980). Most species seem to be predaceous, although some, such as the Kenyan savannah species Tetramorium rothschildi, are known to be granivorous.
Species previously placed in Rhoptromyrmex
Rhoptromyrmex is a widely distributed genus occurring in the tropics of the Afrotropical, Oriental, and Indo-Australian regions, though comparatively species-poor with just ten described species (Brown, 1964; Bolton, 1986; Taylor, 1992). Also, it seems to be comparatively scarce and sporadic on a local level (Brown, 1964). Five species occur in the Afrotropical region, distributed across the whole continent and two species are found in Kenya. The taxonomy of the genus was well examined in the past (Brown, 1964; Bolton, 1976, 1986) and a good identification key to all castes is available.
Members of this genus are ground nesting ants, which build their nests in the soil, beneath rocks, or under the bark of rotten logs (Brown, 1964; Bolton, 1986). They are epigaeic, generalistic foragers that gather dead or living arthropods, consume homopteran honeydew and feed on plant nectaries (Brown, 1964). Furthermore, a few species possess workerless, inquiline females, which parasitize other epicageic ants and other unusual nest founding strategies, e.g. autoparasitism and colony fission, are also known (Bolton, 1986; Taylor, 1992).
The genus Anochetus is widely distributed throughout the tropics and subtropics around the globe (Brown, 1978) and at present comprises 95 valid species (Bolton, 2012). The Afrotropical region holds 24 species of Anochetus (Robertson, 2000), of which nine are listed for Kenya, with two unidentifiable morphospecies from Kakamega and Arabuko Sokoke. The taxonomy of the genus was revised by Brown (1978), who also provided a species-level key.
The members of this genus are comparatively small ponerines living in small colonies with less than 100 workers, which prefer leaf-litter, rotten twigs or logs, crevices in bark, or small excavations in the soil as nesting sites (Brown, 1978). Most Anochetus species are forest inhabitants but several species are highly adapted to arid environments. The whole genus is surely predaceous, and their hunting strategy was described by Brown (1978) as waiting-and-ambush tactics to secure the prey with their trap-jaw-mandibles. Interestingly, Brown (1978) also mentioned the ability of Anochetus to "jump" backwards by snapping their mandibular apices against larger, smooth objects.
The genus Centromyrmex is of pantropical distribution, although, it is most diverse in the Afrotropical region, which has ten species out of the 15 worldwide (Bolton & Fisher, 2008b). Nevertheless, only one species, Centromyrmex sellaris, was found in Kenya so far (Hita Garcia et al., 2009). The taxonomy of the genus is in a good condition due to a recent revision by Bolton & Fisher (2008b), who also provided a new species identification key.
The members of this small genus all appear to be highly specialised, obligate termite predators (Kempf, 1967; Dejean & Fénéron, 1999; Bolton & Fisher, 2008b). The specialisation towards this hypogaeic lifestyle, often in termitaries in close proximity to their prey, is clearly observable in their morphology. They possess a blind worker caste and the middle and hid legs are modified for digging with sclerotised, stout spiniform traction setae on the mesotibiae, meso- and metabasitarsi.
Hypoponera is distributed worldwide, although it reaches its highest diversity in the tropics. Currently, a total of 142 valid species is listed by Bolton (2012). Recently, Bolton and Fisher (2011) revised the taxonomy of the genus for the West Palaearctic and Afrotropical regions, which was in a state of utter confusion and they listed 56 species for the Afrotropical region. All the 15 Kenyan species are easily recognisable on the basis of the latter study. Most species seem to be restricted to the Kakamega Forest and its surroundings, but this could be due to a sampling artefact.
Although Hypoponera is a species rich and common genus in most of the Afrotropical region, little is known about its biology. Species nest and forage in leaf litter, in rotten wood, or in soil (Bolton & Fisher, 2011) and seem to be predators of other arthropods, although there is only limited evidence for this (Levieux, 1983). However, stable isotope data from several Hypoponera species occurring in the Kakamega Forest seem to support this assumption (G.F., unpublished data).
Leptogenys has 216 species (Bolton, 2012) distributed throughout the world tropics and, with 56 valid species, is relatively species-rich in the Afrotropical region (Arnold, 1915, 1922; Bernard, 1953; Bolton, 1975a). For Kenya we list just six species and three morphospecies. Most Leptogenys are nocturnal and thus are often underrepresented in samples (Belshaw & Bolton, 1994). As a consequence, the real number of Kenyan species might very well be much higher. Bolton (1975a) revised the Afrotropical species and provided a species-level key.
These ponerines usually nest in leaf litter, in the ground, in rotten wood, or sometimes in the vegetation (Bolton, 1973a). Bolton (1973a) mentioned that Leptogenys are predatory ants, which mainly hunt termites or isopods. As mentioned above, many species are nocturnal and therefore often difficult to collect or observe.
The genus Odontomachus mainly occurs in tropical and subtropical areas but some species can also be found in temperate zones or even in semi-desert areas (Brown, 1976). Sixty-six species are known (Bolton, 2012) that are equally distributed in the New and the Old World, but surprisingly, only two of them occur in the Afrotropical region. Both species are also present in Kenya and they can be easily distinguished with the species key in Brown (1976).
Species of Odontomachus are large, often conspicuous ants that are mainly predaceous (Brown, 1976; Fisher & Smith, 2008). Like Anochetus, they are trap-jaw ants and can also use these specialised mandibles to jump away if they feel disturbed (Brown, 1976). They hunt other arthropods, often termites, but a few also tend hemipterans. They generally nest in the soil, the leaf litter, or in rotten logs while few species live arboreally (Brown, 1976).
Pachycondyla s.l. is a cosmopolitan genus and, with around 250 species, is comparatively species-rich (Bolton, 2012). The Afrotropical region holds approximately 50 described species (Robertson, 2000) and 17 species, six subspecies and three unidentifiable forms are known from Kenya. Despite the high species richness, good availability of material in museum collections, the conspicuous morphology and behaviour, the African Pachycondyla have never been fully or partly revised. Studies with diagnostic data or identification keys are not available causing the identification to species level to be highly problematic. Also, Pachycondyla did, until recently, represent a morphologically extremely variable genus with many former genera listed as junior synonyms (Bolton, 2012). Molecular evidence indicates that it is not a natural, monophyletic group (Schmidt and Shattuck, 2014). The genus has been divided into several smaller and better defined genera.
Most Pachycondyla s.l. species live in the ground or the leaf litter while some are arboreal (Bolton, 1973a). All species seem to be predacious, often highly specialised (Hölldobler & Wilson, 1990). They mainly hunt alone or in small groups, but especially species, which are specialised to hunt social insects, conduct group raids.
Phrynoponera is a small ponerine genus with just five known species, which are all endemic to the Afrotropical region (Bolton, 2012). Two species are known from Kenya (Bolton & Fisher, 2008a; Hita Garcia et al., 2009), one from the Kakamega Forest in Western Kenya and one from the dry forests at the coast. Wheeler (1922) reviewed the genus, but recently Bolton & Fisher (2008a) provided the first complete taxonomic revision of the known species with a good identification key to the worker caste.
Members of this genus can be mainly found in forested areas and most seem to nest in or under rotten wood, in compacted soil, or in termitaries (Bolton & Fisher, 2008a). Although common on a local scale, these ants are rarely abundant in litter samples (Belshaw & Bolton, 1994; Bolton & Fisher, 2008a). Feeding behaviour is to a great extent unknown, but some species might be termitophagous to an unknown extent (Bolton & Fisher, 2008a).
Platythyrea is a ponerine genus with a wide distribution range found in tropical and subtropical areas around the world. At present, a total of 38 described species is known (Bolton, 2012). One third of these occur in the Afrotropical region and five species are listed for Kenya. The taxonomy is in a comparatively good condition. Brown (1975) revised the genus on a worldwide base and provided a list of the Afrotropical species and a key to the worker caste.
One of the three Kenyan species, Platythyrea modesta, is comparatively well-studied for an African ant species. It lives in polygynous colonies with approximately 50 workers and the nests are placed in pre-existing cavities in the bark or in dead branches of trees, or in termitaries of Cubitermes at the base of trees (Djieto-Lordon et al., 2001). This species is predaceous, generally hunting solitarily for insects like termites or grasshoppers and single workers are able to catch considerably large prey (Djieto-Lordon et al., 2001). Other species of Platythyrea nest in hollow twigs, rotten wood, in termitaries, or in the ground (Brown, 1975).
With 16 species this genus is comparatively small and is restricted to the Afrotropical region (Bolton, 2012). Most are distributed in the rainforests of West and Central Africa (Bolton, 1974b) and three species occur in Kenya. The taxonomy is in an excellent condition due to several revisions and additional species descriptions published in the last decades (Bolton, 1974b; Bolton et al., 1979; Villet et al., 1999; Bolton & Brown, 2002; Fisher, 2006). Especially the revision of the genus by Bolton and Brown (2002) provides good species identification tools, although one has to consider the later described species by Fisher (2006).
Plectroctena are often cryptic or hypogaeic ants that nest in the earth or in rotten logs (Arnold, 1915) and are known to be specialised predators of millipede adults and eggs (Bolton, 1974b; Levieux, 1972). Some species complement their food with beetles or other soft-bodied arthropods (Arnold, 1915).
The genus Psalidomyrmex is restricted to the wet forest zones of tropical Africa and with only six described species is very species-poor (Bolton, 1975b). Only one species, Psalidomyrmex procerus, is known from Kenya. The taxonomy is in a superb condition. A revision of the whole genus, with a key to the workers can be found in Bolton (1975b) and additionally, an updated list of species and a key to workers was published by Bolton & Brown (2002).
Species of Psalidomyrmex nest in rotten wood, beneath logs, or directly in the ground and hunting is generally performed solitarily (Bolton, 1975b). All species seem to be specialised predators of earthworms up to a length of 10 cm (Dejean et al., 1999).
The genus Discothyrea occurs in the tropics and subtropics around the world and 32 valid species are known (Bolton, 2012). Seven of these are found in the Afrotropics (Brown, 1958a), although there is a considerable number of unidentifiable and possibly undescribed, species in several museum collections. The taxonomy of the genus is in an awful condition. No modern revision or species identification key exists, and in his discussion of the African species Brown (1958a) questioned the species status of several species. Consequently, this small genus would highly benefit from a modern taxonomic treatment that considers the difficult species boundaries mentioned by Brown (1958a). We recognise two valid species and four morphospecies from Kenya.
The members of this genus are all small, relatively cryptic ants that nest preferably in rotten wood, in leaf litter, or under stones (Brown, 1958a; Bolton, 1973a). Brown (1958a) first mentioned the possibility that they could be specialised predators of arthropod eggs since the closely related genus Proceratium shows such a trophic specialisation, and was able to find evidence for his theory on the basis of observations of an Australian Discothyrea species (Brown, 1958b). Most studied species prefer spider eggs, although one species of Discothyrea was found in the nests of other ants (Brown, 1980).
The genus Probolomyrmex is of pantropical distribution and is generally very rare as pointed out by several authors (Taylor, 1965a; Agosti, 1994; O'Keefe & Agosti, 1997; Ito, 1998; Fisher, 2007). Fisher (2007) reported the collection of just 25 specimens from nine localities despite the intensive use of several collecting methods with thousands of sampling events in most of Madagascar, and we confirm this with similar experiences from my own studies in Western Kenya. This scarcity of material was already a challenge for the first global taxonomic revision that dealt with just 57 specimens belonging to nine species (Taylor, 1965a). Since Taylor's (1965a) revision further new species have been described (e.g. Agosti, 1994; O'Keefe & Agosti, 1997; Eguchi et al., 2006; Fisher, 2007; Bolton, 2012), but none from any African locality. The current global species count is 20 and three of these occur, patchily distributed, in Sub-Saharan Africa (Taylor, 1965a). One species, Probolomyrmex guineensis Taylor, was recently found in the Kakamega Forest (Hita Garcia et al, 2009).
Ants of this cryptic genus usually appear to nest in litter or in rotten wood, but most of its biology is still unknown. However, one Asian species seems to be a specialised predator of millipedes (Ito, 1998), though it remains unclear if the other genus members prefer the same diet.
Proceratium is a genus of rarely sampled ants that are irregularly distributed in all zoogeographical regions (Baroni Urbani & De Andrade, 2003). Despite its rarity in collections, there are 78 recognised species worldwide, of which just six are found in the Afrotropical region (Baroni Urbani & De Andrade, 2003; Bolton, 2012). The endemic Proceratium toschii is the only described species found in Kenya (Baroni Urbani & de Andrade, 2003), although there are two additional unidentified morphospecies from the Kakamega Forest and Arabuko Sokoke. The taxonomy of the genus is in a satisfactory state because it was monographed by Baroni Urbani & De Andrade (2003) on a global basis. They provided a key to the Afrotropical species, which works very well.
Most Proceratium nest in rotten wood, the ground, under stones, or in trees and colonies appear to be comparatively small with usually less than 200 individuals (Brown, 1974; Baroni Urbani & de Andrade, 2003). Their diet seems to be fairly similar to the one of Discothyrea since both are specialised predators of arthropod’s eggs, mostly spider eggs (Brown, 1958b, 1980).
Approximately 130 species of Tetraponera are known (Bolton, 2012), distributed in the tropical and subtropical regions of the Old World (Ward, 1990). Up to forty of them occur in the Afrotropical region and we list eight species and two subspecies from Kenya. We also examined two morphospecies sampled in the Kakamega Forest, which are most likely undescribed (P.S. Ward, personal communication). In the generic revision of Ward (1990) a species list is provided. In Ward (2006) five species groups for the Afrotropical species were established and one of these was revised to species level. However, species-level revisions for the other groups are not available yet.
Tetraponera occurs in both moist forests and more arid or semi-arid environments (Ward, 2006). All species are arboreal and live either in dead twigs or branches, in insect-bored cavities, or domatia of living plants (Ward, 1991). If the latter is the case, then they life in close association with these plants, which they protect against herbivores (Ward, 1991).